Cracking foam preparations have already been disclosed in, for example, Japanese Patent Application Publication Gazette No. (Sho.) 45-32053 and Japanese Patent Application Laid-Open Gazettes Nos. (Sho.) 63-141910, (Sho.) 63-141917 and (Sho.) 63-141917. Each of these cracking foam preparations employs a combination of a polyoxyethylene polyoxypropylene alkyl ether as an emulsifying agent and dichlorotetrafluoroethane (flon 114) as a propellant as a result of extensive studies on the emulsifying agent and propellant suitable for cracking foam preparations. This is because different combinations give preparations poor in the state of foaming and cracking sound and the use of flon 114 was not regulated at all at that time. Meanwhile, other studies have been made on the use of propane or isobutane alone or liquefied petroleum gas which is a mixture of propane, n-butane, isobutane and the like, as the propellant for cracking foam preparations. However, none of them could give a cracking foam preparation due to its low boiling point. The preparation of the present invention contains n-butane having a high boiling point as a propellant and is completely free from fluorocarbon gases and further it does not contain polyoxyethylene polyoxypropylene cetyl ether which is the most suitable emulsifying agent for flon 114. Thus, the preparation of the present invention is quite different from those of the prior art.
Recently, it has been found that fluorocarbon gases deplete the ozonosphere. Therefore, a worldwide agreement to regulate the use of fluorocarbon gases has been made from the standpoint of preventing environmental disruption and has come into effect in July, 1989. Further, the regulation of fluorocarbon gases will be tightened in the future, though stepwise, to finally abolish the use of fluorocarbon gases completely until the end of this century. Accordingly, it is an urgent requirement to develop a propellant for an aerosol preparation substituting fluorocarbon gases. However, the development of a propellant substituting flon 114 which is the most suitable gas for cracking foam preparations is so difficult that it is inevitable to use liquefied petroleum gas instead of flon 114. However, liquefied petroleum gas is too different from flon 114 in respect of physical properties such as specific gravity and boiling point to give a cracking foam preparation when the emulsifying agent according to the prior art is used. Particularly, when l-menthol, glycol salicylate or methyl salicylate is used as an active ingredient, no preparation acceptable in respect of both emulsifiability and cracking sound could be obtained due to an increased amount our the oil-phase components.
An object of the present invention is to provide a cracking foam preparation excellent in the state of foaming and cracking sound without using flon 114 as a propellant.